Exploring Optical and Electronic Properties of 2D Lead-Free Hybrid Perovskites Based on Sn-Ge for Photovoltaic Applications

2D perovskites have recently become a promising substitute for 3D structures. In 2D lead-free perovskites, unique optical and electronic properties for photoelectronic and photovoltaic applications have been observed due to the quantum confinement effect. In this study, density functional theory calculations were used to examine both the electrical and optical characteristics of lead-free, 2D compounds of (PEA)(2)MI4 (PEA = C6H5C2H4NH3+, M = Ge, Sn, Sn0.5Ge0.5). The results of our research have shown that (PEA)(2)GeI4, (PEA)(2)SnI4, and (PEA)(2)Sn0.5Ge0.5I4 have a direct bandgap of about 1.0 eV, 1.2 eV, and 1.4 eV, respectively. By adding Sn to structure (PEA)(2)GeI4, it was possible to notice a redshift of the absorption edge and band gap shrinking in the visible light range, which demonstrates the special optical characteristics of structure (PEA)(2)Sn0.5Ge0.5I4 for photovoltaic applications. It is revealed that (PEA)(2)Sn0.5Ge0.5I4 compound has a suitable bandgap and high optical absorption and conductivity in the visible region. In addition, low reflectivity, high absorption, high conductivity, and high dielectric constant imply that these materials have a high potential for use in photovoltaic and optoelectronic devices, including optical detectors, LED, solar cells, etc.